So you recovered 9.68g of crystals from your solution. Your calculation was correct. However, I do not know the composition of the crystals or the amount of KNO3 you started out with, so I cannot tell you the percent composition. What I can tell you is that the percent KNO3 recovered is (mass of KNO3 recovered)/(mass of original mixture/solute) * 100. For example, if you recovered 9.68g of KNO3 from an unknown solute that was originally 29.78g, the percent KNO3 recovered would be (9.68/29.78) *100=3.51%